OBJECTIVE: To determine the accuracy with which parents can estimate preschool childrenʼs weight using home scales in order to calculate antipyretic dose. DESIGN: Cross-sectional, method comparison study. SETTING AND PARTICIPANTS: 156 preschool children aged 6 months to 6 years recruited from primary care and the community to an antipyretic strategies trial and managed at home. COMPARISON AND OUTCOME MEASURES: Research nurse weight estimate using Seca 835-2 digital paediatric scales compared with parental weight estimate using usual home scales. RESULTS: Parents of 62 (40%) preschool children had home scales. Research scale estimated weights were heavier than home scale weight estimates, with a mean difference of 0.41 kg (95% CI −0.24 to 0.74 kg), with 95% limits of agreement of −2.44 to 1.47 kg. CONCLUSION: Weight can be estimated accurately enough to calculate antipyretic medicine doses by the minority of parents having scales that can be used to estimate their childʼs weight.